Known in the art for the production of an optically active 2-allyloctanoic acid are 1) the process comprising reacting an octanamide compound of camphorsultam, which is an optically active compound, with diisopropyllithium amide, then reacting the product with an allyl halide to introduce an allyl group diastereoselectively into the octanamide moiety at the position 2 thereof, and eliminating the auxiliary camphorsultam group using a peracid or, alternatively, introducing a propargyl group in lieu of the above-mentioned allyl group, followed by reduction thereof to an allyl group (WO 99/58513), and 2) the process comprising optically resolving racemic propynyloctanoic acid by fractional crystallization using optically active phenethylamine and reducing the thus-obtained optical isomer (Japanese Kokai Publication Hei-08-291106), among others.
However, there are a number of problems in putting the above-mentioned process (1) into practice on a commercial scale; for example, camphorsultam, which is a very expensive chiral auxiliary group, is required, the allylation or propalgylation reaction is to be carried out at a very low temperature of −78° C., and hydrogen peroxide is required to eliminate the auxiliary camphorsultam group. As for the prior art process (2), the optical resolution efficiency is low and, for obtaining 2-propynyloctanoic acid having a sufficiently high optical purity for use as an pharmaceutical intermediate, in particular, a plurality of repetitions of fractional crystallization are required, which inevitably results in a reduction in yield.